Yoshimitsu Okazaki

Corrosion resistance, mechanical properties, corrosion fatigue strength and cytocompatibility of new Ti alloys without Al and V

The effects of various metallic ions using various metallic powders on the relative growth ratio of fibroblasts L929 and osteoblasts MC3T3-E1 cells were carried out. Ti, Zr, Sn, Nb and Ta had evidently no effect on the relative growth ratios of cells. Otherwise, Al and V ions exhibit cytotoxicity from a concentration of > or = 0.2 ppm. This Al effect on cells tend to be stronger in medium containing small quantity of V ions (< or = 0.03 ppm). The new Ti-15%Zr-4%Nb-4%Ta-0.2%Pd alloy exhibited a higher corrosion resistance in physiological saline solution. The addition of 0.02%O and 0.05%N to Ti-Zr alloy improved the mechanical properties at room temperature and corrosion fatigue strength. The relative growth ratios for the new Ti alloy plate and the alloy block extraction were unity. Further, the relative growth ratios were almost unity for the new Ti alloy against apatite ceramic pins up to 10(5) wear cycles in Eagles MEM solution. However, there was a sharp decrease for Ti-6%Al-4%V ELI alloy from 3 x 10(4) wear cycles as V ion was released during wear into the wear test solution since the pH of the Eagles MEM increases with increasing wear cycles.

Corrosion resistance and corrosion fatigue strength of new titanium alloys for medical implants without V and Al

The corrosion resistance and the corrosion fatigue strength of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N and Ti-15Sn-4Nb-2Ta-0.2Pd-0.2O alloys were compared with those of Ti-6Al-4 V extra low interstitial (ELI), Ti-6Al-2Nb-1Ta, pure Ti grade 2 and β type Ti-15%Mo-5Zr-3Al alloys. Anodic polarization and corrosion fatigue testings were performed in various physiological saline solutions at 310 K. The corrosion fatigue test was carried out under the condition of a tension to tension mode with a sine wave at a stress ratio of 0.1 and at a frequency of 10 Hz. The tensile properties of these alloys were measured at room temperature. n nThe change in current density was small up to passivity zone in 1 wt.% lactic acid, PBS(−), calf serum and eagles MEM + fetal bovine serum solutions except 5 wt.% HCl. The current density of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N alloy at potential up to 5 volt tend to be lower than that of Ti-6Al-4V ELI. Otherwise passive current density of the β type Ti-15Mo-SZr-3Al alloy was higher than that of α + β type alloys. The passive films formed on Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O alloy in the calf serum consisted mainly of TiO2, ZrO2, Nb2O5, Ta2O5 and Pd or PdO as demonstrated using X-ray photoelectron spectroscopy. n nThe cycle to failure of Ti-15Zr-4Nb-4Ta-0.2Pd-0.2O-0.05N and Ti-15Sn-4Nb-4Ta-0.2Pd-0.2O alloys annealed at 973 K for 7.2 ks increased with decreasing applied maximum stress. The fatigue strength at 108 cycles in those alloys was about 600 MPa. The fatigue strength of Ti-6Al-2Nb-1Ta alloy at 108 cycles was about 700 MPa. The fatigue strength of β type Ti-15Mo-5Zr-3Al alloy at 107 cycles was lower than that of α + β type alloys.

Cytocompatibility of various metal and development of new titanium alloys for medical implants

The cytocompatibility of new Ti alloys not containing Al and V such as Ti-15%Zr-4%Nb-4% Ta-0.2%Pd-0.05%N-0.2%O and Ti-15%Sn-4%Nb-2%Ta-0.2%Pd-0.2%O were investigated by comparing with those of pure Ti grade 2 and Ti-6%>Al-4%V ELI (Extra Low Interstitial) alloys. The relative growth ratio for the medium extraction of Al containing very little V ions (less than 0.02 mass ppm) was too low as compared to that of V free Al extraction. However, mixed powder extraction such as Ti + Zr + Nb + Ta and Ti + Sn + Nb + Ta exhibited evidently no effect on the relative growth ratio of L929 cells. The relative growth ratios of both L929 and MC3T3-El cells for the new Ti alloys were almost equal to 1 and were slightly higher than pure Ti grade 2 and Ti-6%Al-4%V ELI alloys. Also, the influence of extracting with Eagles minimum essential medium (MEM) solution for L929 cells and ultra pure water for MC3T3-El cells on the relative growth ratio of cells were examined. Further, wear tests were conducted with the new Ti alloys, pure Ti grade 2 and Ti-6%nAl-4%V ELI alloy disks against apatite ceramics and alloy pins in Eagles MEM solution. The relative growth ratios of L929 and MC3T3-E1 cells were estimated with these wear test solutions. The relative growth ratio of L929 cells were almost equal to 1 for the new Ti alloys and pure Ti grade 2 against apatite ceramics pin up to 10 5 cycles. However, the relative growth ratios of L929 and MC3T3-E1 cells sharply decreased for Ti-6%Al-4%V ELI disk against apatite ceramics pin from 3 x 10 4 wear cycles. It was observed that the pH of the Eagles MEM solution gradually increased as the number of wear cycles increased in all the cases of alloy disk against apatite ceramics pin. Also, the V ion concentration increased as the number of wear cycles increased. This result was also similar for MC3T3-El cells. Further, the relationship between metallic concentration in the medium extracted with Ti, Al, V, Zr, Sn, Nb, Ta, and Pd powders and the relative growth ratios of L929 and MC3T3-E1 cells were evaluated. A similar dependence of the concentration of vanadium ion and the relative growth ratios of L929 and MC3T3-E1 cells were seen as in the case of the wear tests.

Surface analysis of Ti–15Zr–4Nb–4Ta alloy after implantation in rat tibia

A new Ti-15Zr-4Nb4Ta alloy without V was implanted in rat tibiae for 6-48 weeks. The new bone formation surrounding the Ti implant in bone marrow, surface analysis of the Ti alloy after implantation, and metal concentrations in dried bone tissue containing new bone were investigated. New bone was well formed around the Ti-15Zr-4Nb-4Ta alloy implanted in bone marrow. The mean thickness of the new bone increased up to 24 weeks after implantation, and changes in the mean thickness thereafter, up to 48 weeks. were very small. The number of corrosion pits observed in the Ti-6Al-4V extra low interstitial (ELI) alloy surface tended to be slightly more than that of the Ti-5Zr-4Nb-4Ta alloy implant. The concentrations of metal elements in the bone tissue containing the new bone tended to increase slightly more than in bones without the implant.

A New Ti–15Zr–4Nb–4Ta alloy for medical applications

Abstract V ions exhibit cytotoxicity in a culture medium from concentrations of ≧0.2 mg/L. Ti, Zr, Nb and Ta are biocompatible elements. A new Ti–15Zr–4Nb–4Ta alloy for medical implants is being developed. Its microstructure, mechanical properties, corrosion resistance and corrosion fatigue properties in a physiological saline solution, biocompatibility with cultured cells, new bone tissue response through rat tibia implantation and surface modification are discussed. Medical applications will be also addressed.

Cytocompatibility of new Ti alloy without Al and V by evaluating the relative growth ratios of fibroblasts L929 and osteoblasts MC3T3-E1 cells

Abstract The cytocompatibility of new Ti alloys not containing Al and V such as Ti-15Zr-4Nb-4Ta-0.2Pd-0,05%N-0.2%O and Ti-15Sn-4Nb-2Ta-0.2Pd-0.2%O were investigated by comparing with those of pure Ti grade 2 andTi-6%Al-4%V ELI (extra low interstitial) alloys. The relative growth ratios of both L929 and MC3T3-E1 cells for the new Ti alloys were almost equal to 1 and were slightly higher than pure Ti grade 2 and Ti-6Al-4V alloys. Also, the influence of extracting conditions with E-MEM solution and ultrapure water on the relative growth ratio of cells were examined. Furthermore, the relationship between metallic concentration in the medium extracted with Ti, Al, V, Zr, Sn, Nb, Ta and Pd powders and the relative growth ratios of L929 cells were evaluated. The relative growth ratio for the medium extraction of Al, containing very little V ions (less than 0.02 ppm) tend to be too low as compared to that of V free Al extraction. However, extraction of Ti, Zr, Sn, Nb and Ta powders, and mixtures of powders such as Ti + Zr + Mb + Ta and Ti + Sn + Nb + Ta had evidently no effect on the relative growth ratio of L929 cells.